Canine dilated cardiomyopathy: lymphocyte and cardiac alpha1- and beta-adrenoceptor concentrations in normal and affected Great Danes
1999
Re, G. | Bergamasco, L. | Badino, P. | Borgarelli, M. | Odore, R. | Tarducci, A. | Zanatta, R. | Girardi, C.
Serum catecholamine levels and myocardial and lymphocyte adrenergic receptor (AR) concentrations were measured in adult great danes affected by canine dilated cardiomyopathy (DCM) and compared to those of healthy animals. A non-homogeneous population of beta-AR, consisting of beta1-AR and beta2-AR, was observed in healthy (41 and 59%, respectively) and affected (17 and 83%, respectively) dog lymphocytes. Binding assays revealed that total beta-AR, beta1-AR and alpha1-AR were significantly downregulated (P<0.05; P<0.01; P<0.001), both in lymphocyte and myocardial cell membranes of affected dogs. beta2-Adrenergic receptor concentrations were significantly reduced only in lymphocyte and right atrium cell membranes (P<0.05). Downregulation was not associated with alterations in receptor binding characteristics, as no significant differences in Kd values were found. Mean plasma catecholamine levels were significantly higher (P<0.01) in DCM dogs (939 +/- 41) than in normal subjects (348 +/- 32), thus suggesting a sympathetic activation. The present study indicates a condition similar to that observed in human patients affected by DCM and that adrenergic receptors in canine lymphocytes reflect the fluctuation of adrenergic receptor concentrations in the myocardium.
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